Dye-Based Ink Compositions

ABSTRACT

Disclosed is an ink composition that includes a colorant; a water-soluble organic solvent; and a penetrant, where the penetrant may be a hydroxylated pentane. Also disclosed is an ink composition that includes a penetrant that enables the ink composition to maintain a drop weight of at least about 4.5 ng at high operating frequencies of an ink drop generator of the ink-jet printer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/073,442, filed on Mar. 7, 2005.

BACKGROUND

The combination of low cost and high quality output have recently madeink-jet printers a popular alternative to other types of non-impactprinters such as laser printers.

The ink-jet printing process involves the ejection of fine droplets ofink onto a print medium such as paper in response to electrical signalsgenerated by a microprocessor. Typically, an ink-jet printer utilizes apen set mounted on a carriage that is moved relative to the surface of aprint medium. In commercially available ink-jet color printers, such asthe DESKJET™ printer available from Hewlett-Packard Company, a four-penset including cyan, yellow, magenta and black inks is generally employedto achieve the necessary color combinations.

A typical pen includes print heads with orifice plates that have verysmall nozzles (typically 10-50 μm diameter) through which the inkdroplets are ejected. Adjacent these nozzles are ink chambers where inkis stored prior to ejection. U.S. Pat. No. 5,181,045 (incorporated byreference herein) discloses a typical channel between the ink chamberand the nozzle.

Ink drop ejection is currently achieved either thermally orpiezoelectrically. In thermal ink-jet printing, each nozzle isassociated with a resistor element. Each resistor element is in turnconnected to a microprocessor, signals from which direct one or moreresistor elements to heat up rapidly. The heating of the resistorelements causes a rapid expansion of ink vapor that forces a drop of inkthrough the associated nozzle onto the print medium. In piezoelectricink-jet printing, ink droplets are ejected due to the vibrations ofpiezoelectric crystals stimulated by electrical signals generated by themicroprocessor.

Interactions between the ink and pen architecture (e.g., the resistorelement, nozzle, etc.) strongly influence the reliability of penperformance. In addition, interactions between the ink and both thesurface and bulk of the print medium play a key role in determiningprint quality. A significant amount of research has recently beenconducted to produce improved ink compositions for ink-jet printers thatexhibit favorable interactions with both the pen architecture and theprint medium.

There are many demanding performance requirements for colorants and inksused in ink-jet printing. For example, they desirably provide sharp,non-feathered images having good water-fastness, light-fastness andoptical density. Optical density is the degree of darkness and/orspectral reflectance of printed colors.

There is a need for inks which are suitable for both thermal and piezoink-jet printers, have high color strength, and produce images having ahigh light-fastness and water-fastness when printed on a substrate.There have been many attempts by industry to produce fast drying inkswith good bleed control. When surfactants are used for the purpose ofdry-time improvement, one often sees a concomitant bleed controlimprovement, however, often at the expense of print quality—morespecifically, edge acuity. Additionally, the use of surfactants in theink compositions can lead to optical density losses. Thus, a need stillremains for ink compositions for use in ink-jet printing which havefaster dry time as well as maintaining other desirable properties ofsuch inks, such as waterfastness, bleed control, and halo control.

SUMMARY

Briefly described, embodiments of this disclosure include inkcompositions for use in ink-jet printer systems. One exemplary inkcomposition, among others, includes a colorant, a water-soluble organicsolvent, and a penetrant wherein the penetrant is a hydroxylatedpentane. Another exemplary ink composition includes a colorant; awater-soluble organic solvent; and a penetrant that enables the inkcomposition to maintain a drop weight of at least about 4.5 ng at highoperating frequencies of an ink drop generator of the ink-jet printer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosed ink compositions can be better understood withreference to the following drawing. The drawing is not necessarily toscale.

FIG. 1 illustrates results of a drop weight vs. frequency test performedon embodiments of the disclosed ink compositions.

DETAILED DESCRIPTION

Ink compositions are provided. In particular, the embodiments relate tothe use of ink compositions in ink-jet printers at high frequencies.Embodiments also relate to use of the ink compositions in ink-jetprinters at high frequencies and with very little drift in drop weightof the ink compositions. Embodiments of the ink-jet ink compositionswill now be described in detail with particular reference to aqueousink-jet ink compositions and the materials therein.

A. Low Ink Drop Weight

High-resolution print (such as photographic-quality resolution) can beachieved in part by having ink drop generators in an ink-jet printheadeject ink drops having a low drop weight. A low-weight ink drop issmaller and provides a finer resolution print than is achieved withhigher-weight ink drops.

In a working example of the disclosed ink compositions, each ink dropweighs at least about 4.5 nanograms (ng). In another embodiment, the inkdrop weighs from about 4.8-5.3 ng.

B. High Operating Frequency

In general, the ink drop generators operate at a high operatingfrequency in order to maintain an acceptable print speed while using lowweight ink drops. Preferably, this operating frequency is in thekilohertz (KHz) range. This high operating frequency combined with thehigh-density array of drop generators provides improved print speed athigh resolution.

In a working example, ink drop generators have been operated atfrequencies ranging from 2.25 to 60 KHz. In particular, it is desirableto have ink drop generators operate at frequencies ranging from about 35to 60 KHz. Ink drop generators can operated at 40 KHz in printing withan ink drop weight of at least approximately 4.5 ng using an embodimentof the disclosed ink compositions.

C. Ink Compositions

Exemplary embodiments of the ink compositions comprise, by weight (allpercents are by weight and are approximate, unless otherwise indicated)from about 0.01 to 50%, or from about 5 to 25% organic solvents; fromabout 0 to 40%, or from about 0.1 to 7% surfactants; from about 0.01 to5%, or from about 0.01 to 2% penetrant(s); and from about 0.5 to 10%colorant. The remainder of the ink compositions are mostly water;however, other components such as biocides that inhibit growth ofmicroorganisms; chelating agents such as EDTA that eliminate deleteriouseffects of heavy metal impurities; buffers; viscosity modifiers; and/oracrylic and non-acrylic polymers can be added to improve variousproperties of the ink composition.

In one embodiment, the ink composition comprises, by weight, about 18%organic solvents, about 6% surfactants, about 0.01 to 2% penetrant, andabout 4% colorant.

The disclosed ink compositions desirably have certain physicalcharacteristics that enable the drop weight to be maintained at anacceptable level, even at high operating frequencies (e.g., greater than18 KHz). For example, the ink composition can have an electricalconductivity from about 4 mS/cm to 10 mS/cm, or from about 6 mS/cm to 7mS/cm. In one embodiment, the ink composition has a pH from about 6 to9.5, or from about 7.5 to 8.5. The disclosed ink composition can have asurface tension from about 40 dynes/cm to 60 dynes/cm, or from about 45dynes/cm to 55 dynes/cm. It is desirable that the ink composition have aviscosity from about 1 cP to 4 cP, or from about 1.5 cP to 2.5 cP.

D. Ink Composition Materials

1. Organic Solvents

One or more organic solvents can be used to prepare the disclosed inkcompositions. In one embodiment, the organic solvents are water-soluble.Exemplary water-soluble organic solvents suitable for this purposeinclude, for example, aliphatic alcohols, aromatic alcohols, diols,triols, amides, ketones, polyketones or ketoalcohols,nitrogen-containing heterocyclic ketones, ethers, glycol ethers,poly(glycol) ethers, alkylene glycols, polyalkylene glycols, thioglycolscontaining alkylene groups, lower alkyl ethers of polyhydric alcohols,and lactams. The concentration of the organic solvents can range from0.01 to 50 wt %, or from 5 to 25 wt %.

2. Surfactants

One or more water soluble surfactants can be employed in the formulationof a vehicle for the ink. For convenience, examples of surfactants aredivided into two categories: (1) non-ionic and amphoteric and (2) ionic.The former class includes the alkyl polyethylene oxides (PEOs); alkylphenyl PEOs; ethylene oxide/propylene oxide block copolymers; acetylenicPEOs; PEO esters; PEO diesters; PEO amines; PEO amides; and dimethiconecopolyols. U.S. Pat. No. 5,106,416 (which is hereby incorporated byreference herein) discusses many of the surfactants listed above ingreater detail. Amphoteric surfactants such as substituted amine oxidesor members of the octyl dimethyl glycine family of octylaminecholoroacetic adducts are also useful in the disclosed ink compositions.Cationic surfactants such as protonated PEO amines, and anionicsurfactants such as diphenyl sulfonate derivatives like, for example,sodium hexadecyl diphenyloxide disulfonate, and ethoxylated oleoalcoholphosphate esters can also be used.

Non-ionic/amphoteric surfactants are sometimes desired over the ionicsurfactants. Specific examples of surfactants that are preferablyemployed in the disclosed ink compositions include secondary alcoholethoxylate, SURFYNOL™ CT-11, octyl dimethyl glycine, sodium hexadecyldiphenyloxide disulfonate, oleyl triethoxy mono diphosphate,iso-hexadecyl ethylene oxide 20 (available from the ICI Group asARLASOLVE™ 200), and/or amine oxides such as N,N-dimethyl-N-dodecylamine oxide, N,N-dimethyl-N-tetradecyl amine oxide,N,N-dimethyl-N-hexadecyl amine oxide, N,N-dimethyl-N-octadecyl arnineoxide, and N,N-dimethyl-N-(Z-9-octadecenyl)-N-amine oxide. The disclosedink composition comprises by weight from about 0 to 40%, or from 0.1 to7%, surfactants.

3. Penetrant

In addition to the surfactant, or in place of the surfactant, apenetrant can be included in the disclosed ink compositions. Thepenetrant is used to improve the wetting properties for a recordingmedium in order to accelerate ink penetration. The penetrant can also beused in the disclosed ink compositions to maintain the ink drop weightwithin acceptable parameters, even at high operating frequencies of theink drop generator. In one embodiment, the ink composition includes apenetrant that enables the drop weight to be maintained at greater thanor equal to about 4.5 ng at frequencies of about 40 KHz.

Water-soluble organic solvents and surface active agents can be used asa penetrant. In particular, the penetrant can be a low molecular weightpolyol. More specifically, the penetrant can be a hydroxylated pentane.The penetrant can also be a substituted hydroxylated pentane. Thesubstitutions on the hydroxylated pentane can be, for example, an alkylgroup. The alkyl group can be, for example, a methyl group.

The hydroxylated pentane can be either, for example, a pentanediol or apentanetriol. The pentanediol can be, for example, a 1,3-pentanediol ora 1,5-pentanediol. The pentanetriol can be, for example, a1,3,5,-pentanetriol. Specifically, the penetrant can be, for example,3-methyl-1,5-pentanediol; 2-methyl-1,3-pentanediol; 1,5-pentanediol; or3-methyl-1,3,5-pentanetriol.

In one embodiment, the disclosed ink composition comprises by weightfrom about 0.01 to 5% penetrant. In another embodiment, the disclosedink composition comprises by weight from about 0.01 to 2% penetrant.

4. Colorants

Suitable colorants for the disclosed ink compositions include but arenot limited to aqueous dyes such as Direct Blue 86, Direct Blue 199,Direct Yellow 132, Acid Yellow 132, Direct Red 9, Direct Red 32, AcidYellow 23, Acid Blue 185, Acid Blue 9, Acid Blue 15, Acid Blue 25, AcidBlue 40, Acid Blue 92, Acid Blue 104, Acid Blue 113, Acid Blue 158, AcidBlue 193, Basic Blue 3, Direct Blue 86, Direct Blue 199, Reactive Blue49, Reactive Blue 25, Solvent Blue 36. Acid Yellow 17, Acid Yellow 23,Acid Yellow 36, Acid Yellow 42, Acid Yellow 99, Acid Yellow 110, AcidYellow 114, Acid Yellow 151, Direct Yellow 86, Direct Yellow 132,Reactive Yellow 37, Solvent Yellow 21. Acid Red 1, Acid Red 14, Acid Red18, Acid Red 35, Acid Red 73, Acid Red 85, Acid Red 88, Acid Red 97,Acid Red 106, Acid Red 119, Acid Red 131, Acid Red 151, Acid Red 27,Acid Red 17, Acid Red 52, Acid Red 249, Acid Red 289, Basic Red 1,Direct Red 227, Reactive Red 180, Reactive Red 31, Reactive Red, andReactive Red 120.

In addition, suitable colorants for the disclosed ink compositions mayinclude but are not limited to black colorants, and more specifically,towards the black dyes. The black colorant can be a dye and/or a pigmentcolorant. In one embodiment, the black colorant can be a dye includingbut not limited to pacified Reactive Black 31, Direct Black 168, AcidBlack 52, Direct Black 170, Acid Black 1, Acid Black 2, Acid Black 11,Acid Black 17, Acid Black 58, Acid Black 64, Acid Black 194, Acid Black210, Acid Black 234, Direct Black 22, Direct Black 19, Direct Black IJDye, Direct Black 168, Reactive Black 8, Solvent Black 13, Food Black 2,Black 1334 and Black 820 by Avecia Colours Ltd. of Manchester, UK. Anembodiment of the disclosed ink compositions may comprise by weight fromabout 0.5 to 10% dye.

EXAMPLE

In order to further illustrate the disclosed ink compositions, someexemplary compositions are set forth below. Inkjet ink compositions wereprepared as shown in Tables 1 and 2 (all values are approximate weightpercentages): TABLE 1 Component Component Type Weight % of Component3-methyl-1,5-pentanediol penetrant 0.5 1-(2-hyroxyethyl)-2- Solvent 8pyrrolidone 2-pyrrolidone Solvent 8 EDTA free acid chelating agent 0.1Trizma Base buffer 0.2 Proxel GXL ™ [NA] biocide 0.1

TABLE 2 Component Component Type Weight % of Component EthoxylatedGlycerol Humectant 4.3 3-methyl-1,5-pentanediol penetrant 0.52,5-dimethyl-3-hexyne-2,5- Solvent 1 diol 1-(2-hyroxyethyl)-2- Solvent 8pyrrolidone 2-pyrrolidone Solvent 8 EDTA free acid chelating agent 0.1Trizma Base buffer 0.2 Proxel GXL ™ [NA] biocide 0.1

A drop weight vs. frequency test was performed using the ink-jet inkcompositions of Table 1 and Table 2. The results obtained are depictedin FIG. 1. The results shown in FIG. 1 indicate that the change (Δ) indrop weight is acceptable for the embodiments of the ink compositiondisclosed in Tables 1 and 2.

Many variations and modifications can be made to the above-describedembodiments. All such modifications and variations are intended to beincluded herein within the scope of this disclosure and protected by thefollowing claims.

1. An ink composition, comprising: a colorant; a water-soluble organicsolvent; and a penetrant, wherein the penetrant is a hydroxylatedpentane.
 2. The composition of claim 1, wherein the penetrant is chosenfrom a pentanediol or a pentanetriol.
 3. The composition of claim 1,wherein the penetrant is chosen from 1,5-pentanediol; 1,3-pentanediol;or 1,3,5-pentanetriol.
 4. The composition of claim 1, wherein thepenetrant is chosen from a branched 1,5-pentanediol; a branched1,3-pentanediol; or a branched 1,3,5-pentanediol.
 5. The composition ofclaim 1, wherein the penetrant is chosen from an alkyl-substituted1,5-pentanediol, an alkyl-substituted 1,3-pentanediol; or analkyl-substituted 1,3,5-pentanediol.
 6. The composition of claim 1,wherein the penetrant is a methyl-substituted 1,5-pentanediol; amethyl-substituted 1,3-pentanediol; or a methyl-substituted1,3,5-pentanediol.
 7. The composition of claim 1, wherein the penetrantis 3-methyl-1,5-pentanediol; 2-methyl-1, 3-pentanediol; or3-methyl-1,3,5-pentanediol.
 8. The composition of claim 1, wherein thepenetrant comprises about 0.01-5% by weight of the ink composition. 9.The composition of claim 1, wherein the penetrant comprises about0.01-2% by weight of the ink composition.
 10. An ink composition for usein an inkjet printer, comprising: a colorant; a water-soluble organicsolvent; and a penetrant that enables the ink composition to maintain adrop weight of at least about 4.5 ng at high operating frequencies of anink drop generator of the ink-jet printer.
 11. The composition of claim10, wherein the penetrant enables the ink composition to maintain a dropweight of about 4.8 ng to 5.3 ng at high operating frequencies of aprinthead of the ink-jet printer.
 12. The composition of claim 10,wherein the ink composition has an electrical conductivity from about 4mS/cm to 10 mS/cm.
 13. The composition of claim 10, wherein the inkcomposition has an electrical conductivity from about 6 mS/cm to 7mS/cm.
 14. The composition of claim 10, wherein the ink composition hasa pH from about 6 to 9.5.
 15. The composition of claim 10, wherein theink composition has a pH from about 7.5 to 8.5.
 16. The composition ofclaim 10, wherein the ink composition has a surface tension from about40 dynes/cm to 60 dynes/cm.
 17. The composition of claim 10, wherein theink composition has a surface tension from about 45 dynes/cm to 55dynes/cm.
 18. The composition of claim 10, wherein the ink compositionhas a viscosity from about 1 cP to 4 cP.
 19. The composition of claim10, wherein the ink composition has a viscosity from about 1.5 cP to 2.5cP.
 20. The composition of claim 10, wherein the penetrant is3-methyl-1,5-pentanediol, and wherein the ink composition: maintains adrop weight of about 4.8 ng to 5.3 ng at high operating frequencies ofthe ink drop generator of greater than 18 KHz; has a conductivity fromabout 6 mS/cm to 7 mS/cm; has a pH from about 7.5 to 8.5; has a surfacetension from about 45 dynes/cm to 55 dynes/cm; and has a viscosity fromabout 1.5 cP to 2.5 cP.
 21. The composition of claim 10, wherein theoperating frequency of the ink drop generator is from about 35-60 KHz.